The present invention relates to an open-end spinning device comprising a vacuum-loaded rotor housing, a spinning rotor having a rotor cup for rotation at a high speed within the rotor housing, and a conduit plate for closing the rotor housing, the spinning rotor being supported free of axial thrust.
Open-end spinning devices with spinning rotors rotating in support-disk bearings have long been known in the state of the art and are described for example in German Patent Publication DE 32 05 566 A1. These known spinning rotors generally have a rotor shaft supported in the bearing nip of two support-disk pairs and also have a rotor cup fixed on the end of the rotor shaft for rotation at a high speed in a vacuum-loaded rotor housing. Moreover, the rotor shaft often comprises a bearing component of a mechanical thrust bearing on its end opposite the spinning cup. The drive of such spinning rotors is typically accomplished via a tangential belt running the length of the machine.
In the known support-disk bearings, the shafts of the support-disk pairs are arranged with their rotational axes slightly crossed relative to the rotor shaft so that a component of axial force acts during the spinning operation on the rotor shaft to urge the rotor shaft into reliable contact with the thrust bearing arranged on the end of the rotor shaft.
Thus, the crossing of the axes of the support-disk pairs results, in conjunction with a given direction of travel of the tangential belt on the rotor shaft, in an axial force component active in the direction of the thrust bearing. A change in the direction of belt travel is not possible in such an apparatus since such would also result in a reversal of direction of the axial force component on the rotor shaft with the consequence that the rotor shaft would be urged out of contact with its thrust bearing and the spinning rotor would then contact against the cover of the rotor housing.
Subsequently published German Patent Publication DE 197 29 191 A1 describes an open-end spinning device in which the spinning rotor is supported with its rotor shaft in the bearing nip of a support-disk bearing free of axial thrust. In this support-disk bearing, the shafts of the support-disk pairs are arranged parallel to the rotor shaft. The axial positioning of the spinning rotor and of the rotor shaft in the bearing nip of the support-disk bearing is accomplished via a magnetic bearing acting on the end of the rotor shaft. Since the absence of axial thrust in such support-disk bearings makes the bearing independent as regards the direction of drive of the spinning rotor, reversible operation of the spinning rotor is possible both clockwise as well as counterclockwise with such an apparatus.
In addition, the subsequently published German Patent Publication DE 198 19 767.5 teaches an open-end spinning device in which the spinning rotor rotates free of axial thrust in electromagnetic bearings so as to be supported without contact within a bearing housing.
Moreover, German Patent Publication DE 196 03 730 A1 teaches an open-end spinning device comprising a replaceable adapter element in the area of a housing cover, i.e., the so-called conduit plate, which closes the rotor housing. Such a conduit-plate adapter which can be fixed in a replaceable manner in a recess of the conduit plate makes it possible in a simple and smooth manner to react rapidly in case of need to the particular technical spinning conditions. That is, if, e.g. during a batch change, which is often associated with a change of spinning rotor, the geometric conditions have changed in the spinning device, optimum spinning conditions can be reestablished by a simple replacement of the conduit-plate adapter.
Finally, German Patent Publication DE-AS 16 85 905 describes an open-end spinning device for producing S-twisted or Z-twisted yarn. That is, the directly supported spinning rotor of this open-end spinning device can be driven selectively clockwise or counterclockwise. The rotor housing of this known spinning device can be closed by a cover element comprising two separate fiber guide conduits. The two fiber guide conduits can be selectively connected to the output of a drafting device, depending on the direction of rotation of the spinning rotor.
However, this known device has a number of disadvantages which have prevented it from becoming accepted in practice. The high speeds required by modern textile machines can not be achieved permanently with directly supported spinning rotors. Moreover, the entire cover element must be replaced in this known device if, for example, the spinning geometry has changed in the spinning device on account of a change of the spinning rotor. It is correspondingly expensive to keep in stock such cover elements to be completely replaced. In addition, cover elements with two fiber guide conduits have the disadvantage that false air is constantly drawn into the spinning device through the inactive fiber guide conduit not connected to the drafting device, which results in a distinctly elevated consumption of energy of these devices.